T.N.A.C.C.B.P.P. EQ360

We used to have a bunch of customers at the trans shop....bring their car in for a full rebuild after driving it til it won't move any more. Once the trans was out, and the $4K price tag was given, they'd ensure us they wanted to fix it 'just not right yet'. So the car car would sit by the shop for months and months, transmission-less, until we forced them to drag it off. But the worst ones were the people who had you complete the repair then due to some extremely unfortunate and unforeseeable crisis couldn't cough up the money. But they still needed the car to 'get to work' and while they had little money they had an abundance of assurances of prompt payment.....
In most cases, wouldn’t the prudent thing to do would be to buy & pay to install a warrantied rebuilt transmission? Versus paying to rebuild one?